SYNTHESIS AND CRYSTAL-STRUCTURE OF THE BO RATE-PHOSPHATE - ALPHA-ZN-3(BO3)(PO4)

Single crystals of the compound alpha-Zn-3(BO3)(PO4) were obtained at 1050 degrees C by using B2O3, P2O5 and ZnCO3 as starting materials and subsequent cooling to 600 degrees C with 20 degrees C/h. X-ray invest igations on single crystals yield a new crystal structure in the monoc linic space group Cm - (Nr. 8) with a = 972.5(2); b = 1272.0(3); c = 4 87.4(3) pm; beta = 119.80(4)degrees; Z = 4. The structure contains iso lated trigonally planar BO3 and tetrahedral PO4 units which are not jo ined together. Zinc occupies three crystallographically different poin t positions and is trigonal-bipyramidally, tetragonal-pyramidally or d istorted tetrahedrally coordinated by oxygen.